Method of fabricating polishing pad having detection window thereon

ABSTRACT

The present invention provides a method of fabricating a polishing pad having a detection window thereon. A mold having a cavity therein and a transparent thermosetting plastic part that is incompletely hardened are provided. The transparent thermosetting plastic part is disposed in the mold and a high molecular weight foam is injected into the cavity of the mold. The transparent thermosetting plastic part and the high molecular weight foam are hardened at the same time. After the step of demolding is performed, a polishing pad having a detection window thereon is formed. Moreover, the transparent thermosetting plastic part can be designed to have the central portion thicker than its peripheral portion for preventing deformation that is caused by the material difference of the detection window and other portions of the polishing pad.

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims the priority benefit of Taiwanapplication serial no. 91133681, filed Nov. 19, 2002.

BACKGROUND OF THE INVENTION

[0002] 1. Field of Invention

[0003] The present invention relates to a method of fabricating apolishing pad. More particularly, the present invention relates to amethod of fabricating a polishing pad having a detection window thereon.

[0004] 2. Description of Related Art

[0005] For the semiconductor manufacture of integrated circuits, it isnecessary to increase the aspect ratios and the levels of conductivelines in order to increase density of electric components and reduce theproduction cost. For the wafer with multilevel metalization and/or highaspect ratios, it is complex and difficult to achieve goodplanarization. Chemical mechanical polishing (CMP) is so far one of thebest technologies to achieve global planarization for very largesemiconductor integration (VLSI) or even ultra large semiconductorintegration (ULSI). This CMP technology was first proposed by thecorporation IBM in the USA, and applied in the damascene fabrication ofembedded conductive lines.

[0006] In general, chemical mechanical polishing relies on the relativemovement between the resilient and hard polishing pad and the slurry(small particle suspension), acting on the surface of the wafer forplanarization. While the polishing pad moves and presses on the surfaceof the wafer, the abrasive particles in the slurry are pressed to thesurface of the wafer. The friction between the slurry particles and thewafer surface leads to abrasive action (loss) of the wafer, so that theuneven surface of the wafer is planarized and topology of the wafer isrefined.

[0007] A transparent window is usually designed to be disposed within aspecific area of the polishing pad for monitoring the polishingsituations. The user can monitor the abrasive situation and control thepolishing conditions through the transparent window and the platformsetup. Therefore, the transparent window is regarded as the end-pointdetection of the polishing for the polishing pad.

[0008] The prior art method of fabricating the detection window isdescribed in U.S. Pat. No. 5,605,760. In one embodiment, the polishingpad is a transparent sheet made of solid uniform polymer. Alternatively,the polishing pad is opaque and has a transparent window. Thetransparent window is fabricated by casting a rod or plug of thetransparent polymer. This transparent casting is either inserted intothe opaque pad before molding or after molding. If the transparentcasting is inserted into the polishing pad in mold, because thematerials of the polishing pad and the transparent window are different,the contraction difference between the polishing pad and the transparentwindow may cause the transparent window to be distorted or deformed.Even if the transparent window is inserted into the cut of the polishingpad after molding, the incomplete contact between the polishing pad andthe transparent window may cause slurry leakage, thus deteriorating thepolishing quality of the wafer.

[0009] U.S. Pat. No. 5,893,796 discloses a polishing pad having atransparent window. The transparent window is fabricated by placing asolid transparent insert into the bulk molten polishing pad material, sothat the window is integrally molded into the polishing pad. However,the transparent window is made of high polishing resistant materials,while the polishing pad is made of low polishing resistant materials.Therefore, the polishing pad has a higher attrition rate, while thetransparent window wears down (polished) at a lower rate, which createsheight difference between the polishing pad and the detection window andcauses cracking of the polishing pad around the transparent window. Thisheight difference of the polishing pad further leads to non-uniformpolishing on the wafer and defects on the surface of the wafer.

SUMMARY OF THE INVENTION

[0010] The present invention provides a method of fabricating thepolishing pad having a detection window, which can improve the priorproblems, such as distortion or warp, of the transparent window.

[0011] The present invention provides a method of fabricating thepolishing pad having a detection window, for improving the slurryleakage problems resulting from in-complete contact between thepolishing pad and the transparent window.

[0012] The present invention provides a method of fabricating thepolishing pad having a detection window, which increases the polishinguniformity of the polishing pad having a detection window.

[0013] As embodied and broadly described herein, the present inventionprovides a mold having a cavity and a transparent thermosetting plasticpart. The transparent thermosetting plastic part is not completelyhardened. The parent thermosetting plastic part is made of a fullytransparent high molecular weight material or a semi-transparent highmolecular weight material, for example. The transparent thermosettingplastic part can be designed to be round, ellipsoidal, tetragonal or inany other suitable shapes, from the top view. The side surface of thetransparent thermosetting plastic part is designed to be an uneven andrugged surface. The transparent thermosetting plastic part is placedinside the cavity of the mold and a high molecular weight foam isinjected into the cavity of the mold. The transparent thermosettingplastic part and the high molecular weight foam become completely hard(hardened) at the same time. The high molecular weight foam is, forexample, a PU foam. The manufacturing method of the PU foam and relatedparameters have been disclosed in the Taiwanese Application No. 91117406under the same inventors. After demolding, the polishing pad having thedetection window is obtained. There is a uniform attrition (polishing)rate toward either the polishing pad or the detection window.

[0014] As embodied and broadly described herein, the present inventionprovides a mold having a cavity and a transparent thermosetting plasticpart. The transparent thermosetting plastic part is not completelyhardened. The parent thermosetting plastic part is made of a fullytransparent high molecular weight material or a semi-transparent highmolecular weight material, for example. The transparent thermosettingplastic part can be designed to be round, ellipsoidal, tetragonal or inany other suitable shapes, from the top view. The side surface of thetransparent thermosetting plastic part is designed to be an uneven andrugged surface. The transparent thermosetting plastic part is placedinside the cavity of the mold and a high molecular weight foam isinjected into the cavity of the mold. The high molecular weight foam ishardened for a short period. The high molecular weight foam is, forexample, a PU foam. The manufacturing method of the PU foam and relatedparameters have been disclosed in the Taiwanese Application No. 91117406under the same inventors. Afterwards, a high molecular weight materiallayer is injected into the cavity and on the high molecular weight foamin the mold. The transparent thermosetting plastic part, the highmolecular weight foam and the high molecular weight material layerbecome completely hardened (hard) at the same time. The high molecularweight material layer is made of, for example, polyurethane (PU),silicon rubber, polybutyl rubber (PBR), polyvinyl chloride (PVC) latexor polyacrylic acid series (PMMA) latex. In this embodiment, the highmolecular weight foam has a hardness larger (higher) than that of thehigh molecular weight material layer, so that the high molecular weightmaterial layer is used as a buffer layer. After demolding, the polishingpad having the detection window is obtained. There is a uniformattrition (polishing) rate toward either the polishing pad or thedetection window.

[0015] As embodied and broadly described herein, the present inventionprovides a mold having a cavity and a transparent thermosetting plasticpart. The transparent thermosetting plastic part is not completelyhardened. The parent thermosetting plastic part is made of a fillytransparent high molecular weight material or a semi-transparent highmolecular weight material, for example. The transparent thermosettingplastic part can be designed to be round, ellipsoidal, tetragonal or inany other suitable shapes, from the top view. The side surface of thetransparent thermosetting plastic part is designed to be an uneven andrugged surface. The transparent thermosetting plastic part is placedinside the cavity of the mold and an incomplete reactive material iscoated to the side surface of the thermosetting plastic part. Theincomplete reactive material is a thermal adhesive, for example. A highmolecular weight foam is injected into the cavity of the mold. Theincomplete reactive material has a chemical reaction with the highmolecular weight foam, so that the incomplete reactive material, thehigh molecular weight foam and the transparent thermosetting plasticpart become hardened at the same time. The high molecular weight foamis, for example, a PU foam. The manufacturing method of the PU foam andrelated parameters have been disclosed in Taiwanese Application No.91117406 under the same inventors. After demolding, the polishing padhaving the detection window is obtained. There is a uniform attrition(polishing) rate toward either the polishing pad or the detectionwindow.

[0016] In addition, the transparent detection window mentioned in theprevious embodiments can be designed to have a curved bottom. In otherwords, the transparent detection window is thicker in the center andthinner in the rim. This design can help to eliminate the deformationresulting from the material variance of the polishing pad and thedetection window.

[0017] It is to be understood that both the foregoing generaldescription and the following detailed description are exemplary, andare intended to provide further explanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The accompanying drawings are included to provide a furtherunderstanding of the invention, and are incorporated in and constitute apart of this specification. The drawings illustrate embodiments of theinvention and, together with the description, serve to explain theprinciples of the invention. In the drawings,

[0019] FIGS. 1-4 are display views of the process steps for themanufacturing method of the polishing pad with a detection windowaccording to one preferred embodiment of the present invention.

[0020]FIG. 5 is a display side view illustrating the shape of the sidesurfaces of the transparent thermosetting plastic part.

[0021]FIG. 6 is a display view illustrating the side surface of thetransparent thermosetting plastic part, while the side surface is coatedwith an incomplete reactive material.

[0022] FIGS. 7-11 are display views of the process steps for themanufacturing method of the polishing pad with a detection windowaccording to another preferred embodiment of the present invention.

[0023]FIG. 12 is a display view illustrating the side surface of thetransparent thermosetting plastic part, while the side surface is coatedwith an incomplete reactive material.

[0024]FIG. 13 is a display view illustrating the design of thethermosetting plastic part having a thicker center and a thinner border.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0025] FIGS. 1-4 are cross-sectional views of the process steps for themanufacturing method of the polishing pad with a detection windowaccording to one preferred embodiment of the present invention.

[0026] Referring to FIG. 1, a mold 100 having a cavity 102 and atransparent thermosetting plastic part 110 are provided. So far, thetransparent thermosetting plastic part 110 is not completely hardened.The parent thermosetting plastic part 110 is made of, for example, afully transparent high molecular weight material or a semi-transparenthigh molecular weight material. For example, the material of thetransparent thermosetting plastic part 110 is acrylic resin (PMMA),polyurethane (PU), polyvinyl chloride (PVC), epoxy resin or unsaturatedpolyester (UP). The transparent thermosetting plastic part 110 has ahardness ranging from 70 Shore A to 75 Shore D.

[0027] Referring to FIG. 2, the transparent thermosetting plastic part110 is placed inside the cavity 102 of the mold 100. The bottom of thetransparent thermosetting plastic part 110 is in tight contact to thebottom surface of the mold 100. The transparent thermosetting plasticpart 110 is adhered to the mold 100, so as to increase the stability andaccuracy for the following processes.

[0028] Referring to FIG. 3, a high molecular weight foam 120 is injectedinto the cavity 102 of the mold 100 by molding, so that the transparentthermosetting plastic part 110 is surrounded by the high molecularweight foam 120. The transparent thermosetting plastic part 110 and thehigh molecular weight foam 120 become completely hard (hardened) at thesame time. In this embodiment, the injected high molecular weight foam120 fills up the cavity 102. The high molecular weight foam 120 is, forexample, a PU foam. The molding methods include thermoplasticinjection-molding, thermosetting injection-molding (usually reactioninjection-molding), thermoplastic or thermosetting injectionblow-molding, thermo-extrusion molding or other similar methods.

[0029] In order to make sure the transparent thermosetting plastic part110 is in good (tight) contact with the high molecular weight foam 120,the side surface of the transparent thermosetting plastic part 110 isdesigned to be an uneven and rugged surface. From the side view (asshown in FIG. 5), the side surface of the transparent thermosettingplastic part 110 is, for example, in a serrated shape 131, in a wavyshape 133 or a toothed shape 135. Since the side surface of thetransparent thermosetting plastic part 110 is uneven, the total contactarea between the transparent thermosetting plastic part 110 and the highmolecular weight foam 120 is increased, further strengthening theconnection.

[0030] In addition, the transparent thermosetting plastic part 110 canbe designed to be round, ellipsoidal, tetragonal or in any othersuitable shapes, from the top view. Preferably, the transparentthermosetting plastic part 110 is in an ellipsoid shape, from the topview.

[0031] Referring to FIG. 4, after the transparent thermosetting plasticpart 110 and the high molecular weight foam become completely hardened,demolding is performed to remove the polishing pad 140 from the mold100. The transparent thermosetting plastic part 110 within the polishingpad 140 is used as a detection window. There is a uniform attrition(polishing) rate toward the whole polishing pad 140. That is, the highmolecular weight foam 120 in the polishing pad 140 has a polishing rateequivalent to that of the detection window (transparent thermosettingplastic part 110).

[0032] The method of the present invention further comprises coating anincomplete reactive material to the side surface of the transparentthermosetting plastic part 110, for strengthening the attachment of thetransparent thermosetting plastic part 110 and the high molecular weightfoam 120. The incomplete reactive material is, for example, a thermaladhesive 150, as shown in FIG. 6. Because of chemical bonding, thethermal adhesive 150 enhances adhesion of the transparent thermosettingplastic part 110 and the high molecular weight foam 120.

[0033] FIGS. 7-12 are cross-sectional views of the process steps for themanufacturing method of the polishing pad with a detection windowaccording to another preferred embodiment of the present invention.

[0034] Referring to FIG. 7, a mold 200 having a cavity 202 and atransparent thermosetting plastic part 210 are provided. So far, thetransparent thermosetting plastic part 210 is not completely hardened.The parent thermosetting plastic part 210 is made of, for example, afully transparent high molecular weight material or a semi-transparenthigh molecular weight material. For example, the material of thetransparent thermosetting plastic part 210 is acrylic resin (PMMA),polyurethane (PU), polyvinyl chloride (PVC), epoxy resin or unsaturatedpolyester (UP). The transparent thermosetting plastic part 210 has ahardness ranging from 70 Shore A to 75 Shore D.

[0035] Referring to FIG. 8, the transparent thermosetting plastic part210 is placed inside the cavity 102 of the mold 200. The bottom of thetransparent thermosetting plastic part 210 is in tight contact to thebottom surface of the mold 200. The transparent thermosetting plasticpart 210 is adhered to the mold 200, so as to increase the stability andaccuracy for the following processes.

[0036] Referring to FIG. 9, a high molecular weight foam 220 is injectedinto the cavity 202 of the mold 200 by molding, so that the transparentthermosetting plastic part 210 is encircled by the high molecular weightfoam 220 and the cavity 202 is partially filled by the high molecularweight foam 220. The high molecular weight foam 220 is hardened forabout 3-5 minutes. In this embodiment, the high molecular weight foam220 is, for example, a PU foam. The molding methods includethermoplastic injection-molding, thermosetting injection-molding(usually reaction injection-molding), thermoplastic or thermosettinginjection blow-molding, thermo-extrusion molding or other similarmethods.

[0037] Referring to FIG. 10, a high molecular weight material layer 222is injected into the cavity 202 and on the high molecular weight foam220 in the mold 200 by molding. The transparent thermosetting plasticpart 210 is also encircled by the high molecular weight material layer222 and the cavity 202 is fully filled by the high molecular weightmaterial layer 222. The transparent thermosetting plastic part 210, thehigh molecular weight foam 220 and the high molecular weight materiallayer 222 become completely hardened (hard) at the same time. In thisembodiment, the high molecular weight foam 220 has a hardness larger(higher) than that of the high molecular weight material layer 222.Therefore, the high molecular weight material layer 222 is used as abuffer layer. The high molecular weight material layer 222 is made of,for example, polyurethane (PU), silicon rubber, polybutyl rubber (PBR),polyvinyl chloride (PVC) latex or polyacrylic acid series (PMMA) latex.The high molecular weight foam 220 has a hardness ranging from 30 ShoreD to 80 Shore D, while the high molecular weight material layer 222 hasa hardness ranging from 5 Shore A to 60 Shore A, for example. Themolding methods include thermoplastic injection-molding, thermosettinginjection-molding (usually reaction injection-molding), thermoplastic orthermosetting injection blow-molding, thermo-extrusion molding or othersimilar methods.

[0038] In order to make sure the transparent thermosetting plastic part210 is in good (tight) contact to the high molecular weight foam 220 andthe high molecular weight material layer 222, the side surface of thetransparent thermosetting plastic part 210 is designed to be an unevenand rugged surface. From the side view, the side surface of thetransparent thermosetting plastic part 210 is, for example, in aserrated shape 131, in a wavy shape 133 or a toothed shape 135 (as shownin FIG. 5). Since the side surface of the transparent thermosettingplastic part 210 is uneven, the total contact area between thetransparent thermosetting plastic part 210, the high molecular weightfoam 220 and the high molecular weight material layer 222 is increased,further strengthening the connection between the above three.

[0039] In addition, the transparent thermosetting plastic part 210 canbe designed to be round, ellipsoidal, tetragonal or in any othersuitable shape, from the top view. Preferably, the transparentthermosetting plastic part 210 is in an ellipsoid shape, from the topview.

[0040] Referring to FIG. 11, after the transparent thermosetting plasticpart 210, the high molecular weight foam 210 and the high molecularweight material layer 222 become completely hardened, demolding isperformed to remove the polishing pad 240 from the mold 200. Thetransparent thermosetting plastic part 210 within the polishing pad 240is used as a detection window. There is a uniform attrition (polishing)rate toward the whole polishing pad 240. That is, the high molecularweight foam 220 in the polishing pad 240 has a polishing rate equivalentto that of the detection window (transparent thermosetting plastic part210).

[0041] The method of the present invention further comprises coating anincomplete reactive material to the side surface of the transparentthermosetting plastic part 210, for strengthening the attachment of thetransparent thermosetting plastic part 210, the high molecular weightmaterial layer 222 and the high molecular weight foam 220. Theincomplete reactive material is, for example, a thermal adhesive 250, asshown in FIG. 12. Because of the chemical bonding, the thermal adhesive250 can enhance adhesion of the transparent thermosetting plastic part210, the high molecular weight material layer 222 and the high molecularweight foam 220.

[0042] Furthermore, the transparent detection window 110, 210 mentionedin the previous embodiments can be designed to have a curved bottom (asshown in FIG. 13). In other words, the transparent detection window110/210 is thicker in the center and thinner in the rim. This design canhelp to eliminate the deformation resulting from the material varianceof the polishing pad 140/240 and the detection window 110/210.

[0043] In conclusion, the present invention has at least the followingadvantages:

[0044] 1. Since the transparent thermosetting plastic part and the highmolecular weight foam become hardened at the same time, the method ofthe present invention can lessen the distortion or deformation of thetransparent thermosetting plastic part and the high molecular weightfoam resulting from hardening at different time points. The method ofthe present invention for manufacturing the polishing pad having thedetection window can increase planarity of the polishing pad.

[0045] 2. The method of the present invention for manufacturing thepolishing pad having the detection window further comprises coating anincomplete reactive material on the transparent thermosetting plasticpart, in order to enhance adhesion of the transparent thermosettingplastic part and the polishing pad, so that the slurry will not leakfrom the cleavage between the transparent thermosetting plastic part andthe polishing pad.

[0046] 3. In the manufacturing method of the present invention, the sidesurface of the transparent thermosetting plastic part is designed to beuneven and rugged. Since the side surface of the transparentthermosetting plastic part is uneven, the total contact area between thetransparent thermosetting plastic part and the high molecular weightfoam is increased and the adhesion between the two is strengthened. Theshape of the transparent thermosetting plastic part is adjustable.

[0047] It will be apparent to those skilled in the art that variousmodifications and variations can be made to the structure of the presentinvention without departing from the scope or spirit of the invention.In view of the foregoing, it is intended that the present inventioncover modifications and variations of this invention provided they fallwithin the scope of the following claims and their equivalents.

What is claimed is:
 1. A method of fabricating a polishing pad having adetection window thereon, comprising: providing a transparentthermosetting plastic part and a mold with a cavity, wherein thetransparent thermosetting plastic part is not completely hardened;placing the transparent thermosetting plastic part into the cavity ofthe mold; injecting a high molecular weight foam into the cavity of themold, wherein the high molecular weight foam and the transparentthermosetting plastic part become completely hardened at the same time;and performing demolding to remove the mold, so as to obtain thepolishing pad with the detection window.
 2. The method of claim 1,wherein a material of the transparent thermosetting plastic part isselected from the following group consisting of a fully transparent highmolecular weight material and a semi-transparent high molecular weightmaterial.
 3. The method of claim 1, wherein a material of thetransparent thermosetting plastic part is selected from the followinggroup consisting of acrylic resin (PMMA), polyurethane (PU), polyvinylchloride (PVC), epoxy resin and unsaturated polyester (UP).
 4. Themethod of claim 1, wherein the transparent thermosetting plastic parthas a hardness ranging from 70 Shore A to 75 Shore D.
 5. The method ofclaim 1, wherein the transparent thermosetting plastic part has acentral portion thicker than a peripheral portion.
 6. The method ofclaim 1, wherein the high molecular weight foam comprises a polyurethanefoam.
 7. The method of claim 1, wherein the transparent thermosettingplastic part has a shape selected from the following group consisting ofround, ellipsoidal and tetragonal.
 8. The method of claim 1, wherein aside surface of the transparent thermosetting plastic part is an unevensurface.
 9. The method of claim 8, wherein the side surface of thetransparent thermosetting plastic part is configured to have a shapeselected from the following group consisting of a serrated shape, a wavyshape and a toothed shape.
 10. The method of claim 1, wherein thepolishing pad has an attrition rate equivalent to that of the detectionwindow.
 11. A method of fabricating a polishing pad having a detectionwindow thereon, comprising: providing a transparent thermosettingplastic part and a mold with a cavity, wherein the transparentthermosetting plastic part is not completely hardened; placing thetransparent thermosetting plastic part into the cavity of the mold;injecting a high molecular weight foam into the cavity of the mold;forming a high molecular weight material layer on the high molecularweight foam in the cavity of the mold; wherein the high molecular weightfoam, the high molecular weight material layer and the transparentthermosetting plastic part become completely hardened at the same time;and performing demolding to remove the mold, so as to obtain thepolishing pad with the detection window.
 12. The method of claim 11,wherein a material of the transparent thermosetting plastic part isselected from the following group consisting of a fully transparent highmolecular weight material and a semi-transparent high molecular weightmaterial.
 13. The method of claim 11, wherein a material of thetransparent thermosetting plastic part is selected from the followinggroup consisting of acrylic resin (PMMA), polyurethane (PU), polyvinylchloride (PVC), epoxy resin and unsaturated polyester (UP).
 14. Themethod of claim 11, wherein the transparent thermosetting plastic parthas a hardness ranging from 70 Shore A to 75 Shore D.
 15. The method ofclaim 11, wherein the transparent thermosetting plastic part has acentral portion thicker than a peripheral portion.
 16. The method ofclaim 11, wherein the high molecular weight foam comprises apolyurethane foam.
 17. The method of claim 11, wherein a material of thehigh molecular weight material layer is selected from the followinggroup consisting of polyurethane (PU), silicon rubber, polybutyl rubber(PBR), polyvinyl chloride (PVC) latex and polyacrylic acid series (PMMA)latex.
 18. The method of claim 11, wherein the transparent thermosettingplastic part has a shape selected from the following group consisting ofround, ellipsoidal and tetragonal.
 19. The method of claim 11, wherein aside surface of the transparent thermosetting plastic part is an unevensurface.
 20. The method of claim 19, wherein the side surface of thetransparent thermosetting plastic part is configured to have a shapeselected from the following group consisting of a serrated shape, a wavyshape and a toothed shape.
 21. The method of claim 11, wherein the highmolecular weight foam has a hardness larger than that of the highmolecular weight material layer.
 22. The method of claim 21, wherein thehardness of the high molecular weight foam ranges from 30 Shore D to 80Shore D.
 23. The method of claim 21, wherein the high molecular weightmaterial layer has a hardness ranging from 5 Shore A to 60 Shore A. 24.The method of claim 11, wherein the polishing pad has an attrition rateequivalent to that of the detection window.
 25. A method of fabricatinga polishing pad having a detection window thereon, comprising: providinga transparent thermosetting plastic part and a mold with a cavity,wherein the transparent thermosetting plastic part is not completelyhardened; placing the transparent thermosetting plastic part into thecavity of the mold, while a side surface of the transparentthermosetting plastic part is coated with an incomplete reactivematerial; injecting a high molecular weight foam into the cavity of themold, wherein the incomplete reactive material has chemical reactionswith the high molecular weight foam, and wherein the incomplete reactivematerial, the high molecular weight foam and the transparentthermosetting plastic part become completely hardened at the same time;and performing demolding to remove the mold, so as to obtain thepolishing pad with the detection window.
 26. The method of claim 25,wherein a material of the transparent thermosetting plastic part isselected from the following group consisting of a fully transparent highmolecular weight material and a semi-transparent high molecular weightmaterial.
 27. The method of claim 25, wherein a material of thetransparent thermosetting plastic part is selected from the followinggroup consisting of acrylic resin (PMMA), polyurethane (PU), polyvinylchloride (PVC), epoxy resin and unsaturated polyester (UP).
 28. Themethod of claim 25, wherein the transparent thermosetting plastic parthas a hardness ranging from 70 Shore A to 75 Shore D.
 29. The method ofclaim 25, wherein the transparent thermosetting plastic part has acentral portion thicker than a peripheral portion.
 30. The method ofclaim 25, wherein the high molecular weight foam comprises apolyurethane foam.
 31. The method of claim 25, wherein the incompletereactive material comprises a thermal adhesive.
 32. The method of claim25, wherein the transparent thermosetting plastic part has a shapeselected from the following group consisting of round, ellipsoidal andtetragonal.
 33. The method of claim 25, wherein the side surface of thetransparent thermosetting plastic part is an uneven surface.
 34. Themethod of claim 33, wherein the side surface of the transparentthermosetting plastic part is configured to have a shape selected fromthe following group consisting of a serrated shape, a wavy shape and atoothed shape.
 35. The method of claim 25, wherein the polishing pad hasan attrition rate equivalent to that of the detection window.